In the Old Testament, a promise was given of a time when the Spirit would be given to believers (Ezek. 36:26-27). In Luke 3:15-17, John the Baptist talks about baptizing people with water, but how Jesus would baptize with the Holy Spirit. This baptism by the Holy Spirit points to Pentecost. The New Testament makes 7 references to being baptized with the Spirit. Upon careful examination of these texts, I would argue the best way of understanding this term refers to a person simultaneously being given the Spirit at the moment they truly come to faith in the gospel. When John made this statement, people who had faith in God did not have the Holy Spirit.
Towards the end of his ministry, Jesus promised to give the Holy Spirit to his followers (Luke 24:49). Since the first Pentecost Sunday, everyone who has had faith has received the Holy Spirit. So the church had a long era where people had faith and loved God and believed in God but did not have the Spirit of God. Today, everyone who has faith has the Spirit. This is a change in the way how man relates to God, and that change began on the first Pentecost Sunday. And that is why the day matters. The day represents a paradigm shift in God’s plan for salvation and redemption.
Why does having the Holy Spirit matter? Books could be written answering that question, but here are a few brief examples of the purpose of the Holy Spirit.
The Spirit indwells the regenerate believer meaning that the Spirit of God is in a person (Rom. 8:11). The Spirit illuminates which enables the believer to understand God’s will and the scripture (1 Cor. 2:14). The Spirit also convicts people of sin (John 16:7-8). The Spirit guides people in truth, because the Spirit is God and testifies to truth for those who follow and discerning the leading of the Spirit (John 16:13). The Spirit equips people by giving believers Spiritual gifts. Every believer has at least one gift from the Holy Spirit (1 Cor. 12:11). The gifts are meant to be utilized by glorifying God in accordance with people ministering to others and maturing in love and knowledge of God. The Spirit empowers believers by continually progressing them in holiness and into the likeness of Jesus(2 Cor. 3:18).
The Spirit equips believers with gifts for believers in the Church to carry out their ministries for the sake of building up the body of Christ in the Church until the time Jesus returns (1 Cor. 1:7). Once the believer has been equipped with a gift by the Spirit, it is something which the believer has, because the gifts which they have are the unique parts which those individuals are of the body of Christ (1 Cor. 12:12-26).
The Spirit equips with gifts but the Spirit also gives what’s called “fruit.” When the fruit of the Spirit is discussed (Gal. 5:16-26), it is referring to characteristics which are indicators of the Christian life. A significant point of difference between the two is that all Christians have at least one gift. But if there is an area where someone has not been gifted (such as teaching), a believer should not necessarily desire to have that gift. Instead, people should focus on using the gifts which they do have to bring glory and honor to God. With the fruit of the Holy Spirit, those are all qualities which are desirable.